In general, virtual reality can surround and immerse a person in a computer-generated, three-dimensional (3D) environment. The person can enter this environment by interacting with and/or physically wearing specific electronic devices. Example electronic devices can include, but are not limited to, a helmet that includes a screen, glasses or goggles that a user looks through when viewing a screen (e.g., a display device or monitor), gloves fitted with sensors, and external handheld devices that include sensors. Once the person enters the VR environment, the person can interact with the 3D environment in a way (e.g., a physical way) that seems real to the person.